Does MetalReady cause rust?

[sballard]

I've been finishing up some body work by grinding down some welds at the bottom of the rockers. I had some bare metal areas that had a small bit of flash rust. It was just barely noticeable. I thought I would treat the area with Metal Ready last night just to give me the some time before I lay some primer on. Tonight the surfaces are covered with red stuff that must be rust. I rinsed the surface with water after a 15 min application. My recollection from prior use is that the metal surfaces turn dark gray following Metal Ready. What did I do wrong?

[john walker's workshop]

if you leave the stuff on and don't rinse, it phosphate coats. good for storage. you rinsed, so it rusted. you need to metal etch prime real soon after rinse and dry.

[sballard]

Thanks John. That's good to know. I didn't understand that from the directions.